1. Field of the Invention
This invention relates to a cellulose insulation product and method and, more particularly, to a fire-resistant, cellulose insulation product and method wherein talc, in combination with a boron compound, is intimately blended with the cellulose to impart the necessary fire-resistant characteristics to the cellulose.
2. Related Applications
This application is a continuation-in-part application of copending application Serial No. 961,088 filed Nov. 15, 1978 which issued as U.S. Pat. No. 4,230,585 on Oct. 28, 1980.
3. The Prior Art
Recent events relating to the availability and cost of fuels has resulted in an increased interest in insulation products for structures such as dwellings and the like. The primary feature of any insulation is the ability to impede conductive and convective heat losses by forming minute air pockets in a nonconductive or low thermal conductive matrix. The air pockets create an effective dead air space or barrier gainst the conductive and convective heat losses.
A finely divided cellulose material has been found to be extremely useful as an insulation product since the cellulose has very low thermal conductivity and can be shredded or otherwise finely divided to provide the desirable air entrapment characteristics. Suitably treated, the cellulose also maintains a desired degree of dimensional stability referred to in the trade as "loft." Additionally, insulation-quality cellulose is readily available from recycled cellulose products such as newsprint, cardboard and kraft paper. These raw materials are readily recoverable from the waste disposal systems of most communities.
However, cellulose is carbonaceous and a finely divided cellulose product is, therefore, extremely flammable in view of the enormous surface area exposed for combustion. Accordingly, it has been conventional to mix a predetermined quantity of a fire-resistant and/or fire-suppressant material such as a boron compound with the cellulose. The boron compounds generally include boric acid, borax and borates.
Additionally, certain cellulose insulation products have included ammonium sulfate as the fire-resistant and/or fire-suppressant material. However, ammonium sulfate is believed to be deleterious since it combines with moisture to form acidic byproducts which have been found to cause corrosive damage to electrical wiring, etc. Accordingly, recent governmental regulations have required the discontinuance of cellulose insulation products incorporating ammonium sulfate as the fire-resistant and/or fire-suppressant material.
Although cellulose insulation is used only in sheltered locations, exposure to atmospheric moisture is of considerable importance. Conventionally, cellulose insulation is incorporated in a dwelling as an overlayment in the attic above the ceiling and is blown in place. Cellulose insulation has the added advantage of being fluffed by the action of the blowing process. Most attics are ventilated and include exhaust systems from bathrooms, range hoods and the like being directed into the attic space for subsequent dispersal to the atmosphere through the attic ventilation system. Accordingly, moisture in the heavily moisture-laden air from a bathroom or range hood tends to condense on the exposed insulation on cold days. This condensation has been found to form the acidic byproducts from ammonium sulfate resulting in its being proscribed by governmental regulations.
Additionally, other fire-resistant compounds that are soluble are known to "migrate" under the effect of moisture. This migration results from the periodic solubilization upon moisture condensation followed by recrystallization upon subsequent moisture evaporation so that the solubilized compounds are removed from portions of the cellulose. The exposed cellulose is thereby deprived of its fire-resistant protection with a resulting, potentially dangerous condition.
The production of a fire-resistant, cellulose insulation material also requires extensive grinding and mixing of the fire-resistant materials with the cellulose insulation. While various fire-resistant and/or fire suppressant materials have been tried, these materials generally tend to be abrasive to the grinding equipment resulting in excessive equipment wear with corresponding downtime and production loss.
In view of the foregoing, it would, therefore, be a significant advancement in the art to provide a fire-resistant, cellulose insulation material which is (1) relatively available as a raw material and, therefore, relatively inexpensive to obtain, (2) inert to occasional contact with condensation, and (3) low in abrasion of grinding equipment. Such a fire-resistant cellulose insulation material and method is disclosed and claimed herein.